Potential infection of grazing cattle via contaminated water: a theoretical modelling approach.

Wastewater discharge and agricultural activities may pose microbial risks to natural water sources. The impact of different sources can be assessed by water quality modelling. The aim of this study was to use hydrological and hydrodynamic models to illustrate the risk of exposing grazing animals to faecal pollutants in natural water sources, using three zoonotic faecal pathogens as model microbes and fictitious pastures in Sweden as examples. Microbial contamination by manure from fertilisation and grazing was modelled by use of a hydrological model (HYPE) and a hydrodynamic model (MIKE 3 FM), and microbial contamination from human wastewater was modelled by application of both models in a backwards process. The faecal pathogens Salmonella spp., verotoxin-producing Escherichia coli O157:H7 (VTEC) and Cryptosporidium parvum were chosen as model organisms. The pathogen loads on arable land and pastures were estimated based on pathogen concentration in cattle faeces, herd prevalence and within-herd prevalence. Contamination from human wastewater discharge was simulated by estimating the number of pathogens required from a fictitious wastewater discharge to reach a concentration high enough to cause infection in cattle using the points on the fictitious pastures as their primary source of drinking water. In the scenarios for pathogens from animal sources, none of the simulated concentrations of salmonella exceeded the concentrations needed to infect adult cattle. For VTEC, most of the simulated concentrations exceeded the concentration needed to infect calves. For C. parvum, all the simulated concentrations exceeded the concentration needed to infect calves. The pathogen loads needed at the release points for human wastewater to achieve infectious doses for cattle were mostly above the potential loads of salmonella and VTEC estimated to be present in a 24-h overflow from a medium-size Swedish wastewater treatment plant, while the required pathogen loads of C. parvum at the release points were below the potential loads of C. parvum in a 24-h wastewater overflow. Most estimates in this study assume a worst-case scenario. Controlling zoonotic infections at herd level prevents environmental contamination and subsequent human exposure. The potential for infection of grazing animals with faecal pathogens has implications for keeping animals on pastures with access to natural water sources. As the infectious dose for most pathogens is more easily reached for calves than for adult animals, and young calves are also the main shedders of C. parvum, keeping young calves on pastures adjacent to natural water sources is best avoided.

Treatment with Ca(OH)2 for inactivation of Salmonella Typhimurium and Enterococcus faecalis in soil contaminated with infected horse manure.

AIM: To investigate the inactivation of Salmonella enterica serovar Typhimurium and the faecal indicator Enterococcus faecalis in horse manure:soil mixtures by application of hydrated lime (Ca(OH)(2)). METHODS AND RESULTS: In laboratory incubations, the inhibitory effect of different concentrations of Ca(OH)(2), as well as different application techniques, was tested. Other variables were horse manure:soil ratio, incubation temperature (6 and 14°C) and soil type (sand/clay). Bacterial enumeration by the plate count method in samples taken at increasing intervals revealed that Ca(OH)(2) effectively reduced Salmonella Typhimurium numbers. However, to achieve a sufficient reduction, the Ca(OH)(2) had to be applied at a sufficient rate, and the amount required varied because of manure:soil ratio and incubation temperature. The results showed that a pH above 11 was needed and that a high pH had to be maintained for up to 7 days. An appropriate application technique for the Ca(OH)(2) was also important, so that a high pH was obtained throughout the whole material to be treated. In addition, a high manure:soil ratio in combination with a higher incubation temperature was found to rapidly neutralize the pH and to increase the risk of Salmonella re-growth. CONCLUSIONS: Application of Ca(OH)(2) can be an efficient method for treating a Salmonella-contaminated horse paddock. A high pH is a key factor in Salmonella inactivation, and thus, monitoring the pH during the treatment period is necessary. To avoid re-growth excess manure should be removed for separate treatment elsewhere. SIGNIFICANCE AND IMPACT OF THE STUDY: Persistence of Salmonella in horse paddocks poses a risk of disease transmission to healthy animals and people who come into contact with these animals. An efficient method to de-contaminate a Salmonella-contaminated soil would be a valuable tool for animal welfare and for public health.

Application of routines that contribute to on-farm biosecurity as reported by Swedish livestock farmers.

On-farm biosecurity is important for preventing the spread of several contagious animal diseases. In this study, biosecurity routines among Swedish farmers with livestock (cattle, pigs, sheep or goats) were examined through questionnaires posted by mail. Moreover, the use of protective clothing among professionals visiting farms, such as animal transporters and veterinarians, were investigated through assessments made by the farmers. Questionnaires were completed, partly or fully, by 518 farmers (overall response rate 34%). Possible associations between biosecurity routines and livestock species, geographic location and herd size were analysed. Large variations in biosecurity routines were found, both within and between groups, and some farms appeared to have a relatively high level of biosecurity. However, <40% of the farmers reported that they provide protective clothing for visitors, and 50% of farmers buying live animals introduced these directly into the herd without prior isolation. In general, a higher level of biosecurity was reported by farmers with herds with only pigs, when compared to farmers with cattle, sheep/goats or mixed species. A higher level of biosecurity was also reported by larger farms compared to hobby farms. Inconsistent biosecurity routines were reported, which was interpreted as a lack of knowledge of how different infections can spread and how this can be prevented. Furthermore, some replies indicated that the farmers perceived the risk of introduction of disease as low. According to the farmers' assessments, the use of protective clothing among professionals visiting farms varied considerably, both among different professions and within the same profession. On average, veterinarians and artificial insemination (AI) technicians got high scores in this assessment, while salesmen, repairmen and animal transporters were reported to seldom use protective clothing. Based on the findings, there is room for improvement of on-farm biosecurity. There is also a need to further investigate the motivators and constraints for altered routines among both Swedish livestock farmers and professionals visiting farms.